1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device capable of reducing power consumption of a gate driving circuit, and a method for driving the same.
2. Discussion of the Related Art
Recently, as display devices for mobile devices, liquid crystal display devices are widely used due to excellent image quality, weight reduction, slimness and low power consumption.
A Gate In Panel (GIP) type liquid crystal display device, in which a gate driving circuit is mounted in a panel so as to realize a small volume, weight reduction and low manufacturing cost, has been introduced.
In the GIP type liquid crystal display device, the gate driving circuit using a Thin Film Transistor (TFT) formed of amorphous silicon (a-Si) is mounted in a non-display region of a liquid crystal panel. The gate driving circuit includes a shift register for sequentially supplying scan pulses to a plurality of gate lines. The shift register includes an output buffer unit for receiving a clock pulse from a timing controller and outputting the scan pulse and an output control unit for controlling the output of the output buffer unit. The output buffer unit is configured of a plurality of TFT.P=IV=CV2f  Equation 1
At this time, the power consumption of the TFT configuring the output buffer unit is greatest in the gate driving unit. In detail, referring to Equation 1, power consumption P is proportional to current I, voltage V, capacitance C and frequency f. At this time, the output buffer unit receives a clock pulse having a highest driving frequency. In addition, the size of the TFT configuring the output buffer unit is largest in the gate driving circuit and thus the capacitance C of a parasitic capacitor generated between a gate electrode and a drain electrode for receiving the clock pulse is greatest in the TFT. Accordingly, since the TFT configuring the output buffer unit has highest driving frequency f and greatest capacitance C of the parasitic capacitor, the power consumption of the TFT is greatest in the gate driving circuit.
A display device using a gate driving integrated circuit also includes an output buffer unit similarly to the GIP type liquid crystal display device. In the gate driving integrated circuit, the output buffer unit is formed of a polysilicon TFT, and the capacitance C of a parasitic capacitor of the polysilicon TFT is less than that of an amorphous silicon TFT.
Accordingly, since the GIP type liquid crystal display device uses the output buffer unit formed of the amorphous silicon TFT, the capacitance C of the parasitic capacitor is greater than the capacitance of the parasitic capacitor of the display device using the gate driving integrated circuit formed of the polysilicon TFT. As a result, power consumption is increased.